The present invention relates to a powder-actuated fastening tool with a hammer piston and, more particularly, to a pawl for returning the hammer piston in its firing position.
Powder-actuated fastening tools are known in the art wherein cocking is achieved by pressing the tool muzzle against the surface of the material intended for receiving the anchoring member, causing retraction of the pawl, the pawl resuming its idle position during the opening of the apparatus, in order to return the piston to its firing position.
The barrel of such an apparatus is formed with a longitudinal slot and two plane milled surfaces parallel to the barrel axis and connected through a ramp. The pawl of such an apparatus is slidably mounted within a pawl holder fixed to the casing. The pawl is biased to its idle position by resilient means, and comprises bosses shaped for engaging the barrel milled surfaces. The operative end of the pawl projects into the slot and is shaped so as to engage, in its idle position, the piston.
The pawl being in its idle position, that is in the position where the piston is in an upward position, its bosses engage the first milled surface closest to the barrel axis. When the apparatus is pressed against the material, the bosses slide, against the action of the resilient means, from the first milled surface to the second milled surface, which is more remote from the barrel axis than the first, causing the operative end of the pawl to retract so as not to project into the barrel.
For safety reasons, the cocking of such an apparatus is achieved by pressing it against the material intended for receiving the anchoring member. In order to facilitate the handling of the apparatus once a cartridge has been loaded, means may be provided which are arranged in such manner as to maintain the barrel in its closed but non-cocked position. Generally, the closing is resilient, but it requires an extra part such as a clip.